This invention relates to a measuring device which measures required data and converts said measured data into electric signals, and more particularly to a measuring device which is provided with correcting means capable of correcting measured data with a high precision over a broad range of operation.
Measuring means known to date includes transducers for detecting data obtained from, for example, a living body (living body data). One of the known transducers which measures the temperature of a living body is a thermistor transducer. This thermistor transducer raises problems in respect of the linearity of measured data, and the exchangeability of said transducer and its heat time constant. Therefore, a correction circuit is generally attached to the transducer to correct for its properties. Similar difficulties arise with other forms of transducers, which are therefore usually provided with a correction circuit.
FIG. 1 is a schematic block diagram of the above-mentioned conventional transducer-type measuring device applied to a living body data-measuring apparatus. A living body data-detecting transducer 10 is connected to a correction circuit 12 which corrects for the properties of said transducer 10. Both transducer 10 and correction circuit 12 are integrally assembled to jointly constitute a measurement-correcting module 14. An output signal from the correction circuit 12 is amplified by an amplifier 16. The amplified signal is converted into an 8-bit digital signal by an analog-digital (A-D) converter 18. A converted digital signal is transmitted to a display unit 20 to be indicated as measured data based on, for example, the temperature of a living body.
A correction circuit used with the above-mentioned measuring device is generally formed of resistors assembled with capacitors. Therefore, a corrected data obtained at a specified point of the transducer at which correction is to be made is used as a standard. Therefore, the conventional living body data-measuring transducer has the drawback that correction cannot be effected over the broad operation range of the transducer. Further drawbacks of the conventional living body data-measuring transducer are that the correcting property of the correction circuit 12 is affected, for example, by the temperature characteristic of the parts of said circuit 12 and changes with time in the performance of said parts; where the constant of parts is not fixed, such parts have to be provided in large number in order to elevate the correction precision of the correction circuit 12, thereby rendering the entire measuring apparatus bulky and increasing its cost; and if it is attempted to adjust the performance of the correction circuit 12 by trimming during manufacture for elevation of the correction precision of said circuit 12, then the cost of the entire measuring device is further increased.